Discharging gap device for a nagnetic blow-out arrester

ABSTRACT

A discharging gap device for a magnetic blowout arrester comprising a partition plate separating an arc extinguishing chamber into upper and lower sections, a coil-shaped guide electrode extending through said partition plate so that the end portion thereof is led to the underside to portions located in said sections respectively, discharge electrodes juxtaposed to the upper portion and the lower portion of said guide electrode, and a cover closing the chamber.

United States Patent [72] Inventors Fumio Tomura;

Yasukatsu Okino, Shizuoka-ken, Japan [21] Appl. No. 10,924

[56] References Cited UNITED STATES PATENTS 3,159,765 12/1964Schultzetal. 317/74X 3,242,376 3/1966 Schultz 315/36 3,354,345 11/1967Stetson 317/77X 3,515,947 6/1970 Stetson 317/61 Primary Examiner-JamesD. Trammell Attorney-Kelman & Berman ABSTRACT: A discharging gap devicefor a magnetic blowout arrester comprising a partition plate separatingan arc extinguishing chamber into upper and lower sections, a coilshapedguide electrode extending through said partition plate so that the endportion thereof is led to the underside to portions located in saidsections respectively, discharge electrodes juxtaposed to the upperportion and the lower portion of said guide electrode, and a coverclosing the chamber.

Patented A ril 27,1971 3,576,470

2 Sheets-Sheet 1 INVENTORS, 72m u/"q, I fzfsu DIV no AGE/v75 PatentedApril 27, 1971 3,576,470

2 Sheets-Sheet 2 INVENTORS. u m a M" ura.

HGEA/TS,

DISCHARGING GAP DEVICE FOR A MAGNETIC BLOW- OUT ARRESTER The presentinvention relates to a discharging gap device for a magnetic blowoutarrester in which the dynamic current is blown into a narrow chamber toraise the arc voltage so as to throttle and cut off the dynamic current.

Generally, arresters of the prior art rely on magnetic manipulation forblowing the dynamic current into a narrow arc extinguishing chamber toraise the arc voltage, thereby throttling the dynamic current andincreasing the chopping efficiency. To attain the end, the arrestersrequire a magnetic field of very high intensity for manipulating thearc. This makes it necessary to increase the number of turns of theblowout coil built into the arresters, which in turn makes it necessaryto provide means to raise the arc voltage in the protective gap of theblowout coil so that the dynamic current may be branched'ofi as much aspossible to the blowout coil. Moreover, the voltage which the blowoutcoil can withstand (mainly the impact voltage) must be increased. Theseproblems are hard to overcome.

It has hitherto been customary to provide, in an arc extinguishingchamber, a pair of discharge electrodes for forming a discharging gap ora guide electrode for aiding in the movement of the arc. In both ofthese cases, the length of the arc can be increased if the length of theelectrode or electrodes is reduced, but a magnetic field of very highintensity is required for are manipulation.

This invention has as its object the provision of a discharging gapdevice for a magnetic blowout arrester which permits to provide amagnetic field of very high intensity, reduce the number of turns of theblowout coil and reduce the diameter of the chamber.

FIGS. 1a and lb are plan views of electrode arrangements of prior artdevices;

FIG. 2 is an exploded perspective view of a discharging gap deviceaccording to this invention;

FIG. 3 is a connection diagram of the discharging gap device accordingto this invention;

FIG. 4 is a longitudinal sectional view of the arc extinguishing chamberused in the present invention; and

FIGS. 5 to 7 are perspective views showing parts used in the presentinvention, FIG. 5 showing the guide electrode, FIG. 6 a dischargeelectrode and FIG. 7 a rivet for fixing the electrode.

Before describing an embodiment of this invention with reference to thedrawings, prior art devices will be described with reference to FIG. 1to enable the object, construction and operation of the presentinvention to be understood more clearly.

FIG. 1a shows a pair of discharge electrodes 2, 2 mounted in an arcextinguishing chamber 1 to provide a discharging gap therein. FIG. 1badditionally shows a guide electrode 3 mounted for aiding in themovement of the arc. In both examples shown, if a magnetic field isapplied to the chamber 1 from outside in a direction perpendicular tothe plane of the FIG., a magnetic field produced by a current passedthrough the electrodes 2, 2 will be added to the externally appliedmagnetic field, so that the density of the magnetic field is increasedin an area surrounded by the electrodes 2, 2 and the are as indicated bydots. The pressure exerted by the magnetic field causes the arc to movetoward the outer periphery as indicated by arrows. Thus, to increase thedynamic current chopping efficiency requires to extend the arc morerapidly and to a greater length even when the external magnetic field islow in intensity. The results of tests have shown that in the case ofthe electrode arrangement of FIG. 1a, the greater the length of theelectrodes 2, 2, the more rapid is the movement of the arc. Generally,however, the larger the electrodes, the smaller is the length of the arcthat can be produced when the diameter of the chamber is constant. Theresults are more or less the same with the arrangement of FIG. lb. Thus,if the length of the electrodes 2, 2 is reduced, it is possible toincrease the length of the arc in the electrode arrangements shown inFIGS. 10 and 1b but a magnetic field of very high intensity must beprovided for are manipulation.

The present invention has been made with a view to providing a magneticfield of very high intensity, reducing the number of turns of theblowout coil and reducing the diameter of the arc extinguishing chamber.An embodiment of the invention will be described with reference to thedrawings.

FIG. 2 shows a shallow, cylindrical wall 1 of an arc extinguishingchamber. The wall 1 consists of heat resisting insulating material andis integral with an axially central partition plate 11. The plate has acentral tubular portion 14 about an axial bore 12, and an outer,substantially annular portion 13 which axially tapers from itscircumference toward the tubular portion 14. Recesses 15 in the twoopposite faces of the plate portion 13 respectively accommodateelongated discharge electrodes 2. A radial groove 16 in each face leadsoutward to an opening in the chamber wall 1 remote from thecorresponding electrode 2, the two grooves being diametrically oppositeeach other. A radial slot 17 in the plate portion 13 extends from thetubular portion 14 to the chamber wall 1 and connects the two sectionsof the chamber otherwise separated by the plate 11. The plate portion 13has axial openings 18 spacedly adjacent the slot 17.

The discharge electrodes 2, 2 are semicircular in shape as shown in FIG.6 and are mounted on the upper surface and lower surface respectively ofthe partition plate 11 in such a manner that their convex sides aredirected toward the portion 14, and the slot 17 is disposedcircumferentially between the electrodes which are fixed by tubularrivets 4 (FIG. 7) sealed in the openings 18. A rod-shaped guideelectrode 3 has a helical, central portion of one and one-half turnscoiled about the tubular partition plate portion 14 and passing throughthe slot 17. The straight radial ends of the electrode 3 are recieved inthe grooves 16 respectively.

In the assembled condition of the device, the bore 12 receives a spring5 between two cylindrical metal plugs 6 smaller in diameter than thebore. The plugs are held in place by two flat, circular covers 7 ofheat-resisting insulating material which close the axial ends of thechamber and whose outer faces carry electrode plates 8. The electrodeplates 8 are connected in the assembled device by nonillustratedconductors passing through openings in the covers 7 aligned with therivets 4.

Each of the plugs 6 and the associate electrode plate 8 constitute acapacitor, and corona discharge takes place between the plugs 6 and thecovers 7 immediately before the occurrence of discharge.

The capacitors improve the distribution of electric potentials whenseveral discharging gaps are provided. Corona discharge exerts favorableinfluences on the operation of the device when an impact dischargevoltage is applied thereto. In FIG. 3, L designates a blowout coil, gl aprotective gap, and R a dynamic current limiting resistor.

The operation of the device constructed as aforementioned according tothis invention will now be explained. Upon application of animpact'voltage to the arrester, discharge takes place between thedischarge electrodes 2, 2 and the adjacent upper and lower portions ofthe guide electrode 3. A dynamic current which tlows following theoccurrence of discharge is passed through the protective gap gl andblowout coil L to produce a magnetic field in the coil L. Dischargefirst takes place between the substantially central portion of eacharcuate discharge electrode 2 and the guide electrode 3, said centralportion being disposed nearest to the guide electrode of all theportions of each discharge electrode. Then discharge takes place betweenthe two discharge electrodes 2 through the intermediary of the guideelectrode 3. If an arc is formed, a current caused by the arc and acurrent passed through the guide electrode 3 flow in opposite directionsand are disposed in close proximity to each other as shown by arrows inFIG. 2. Thus, magnetic fields are formed by the oppositely directedcurrents in an area closed by the dynamic current. Moreover, themagnetic field produced in the blowout coil L is also applied to saidarea so that the magnetic field in said portion becomes very dense. Thiscauses the arc to be pulled rapidly and with a great force toward theperiphery of the chamber .the impedance is increased. Combined with theaction of the resistor R, this chops the dynamic current. Particularly,if the distance e between the arc current and the guide electrode 3 isreduced, it is possible to boost the chopping effect on the dynamiccurrent. The gas produced after the chopping of the dynamic current isdischarged through the grooves 16 to the outside. It will be readilyunderstood that the device constructed as aforementioned offerssubstantial advantages.

' First, the invention permits to reduce the number of turns of theblowout coil L. if the device of the invention is intended for choppingthe current without boosting the arc voltage, the blowout coil L can beeliminated entirely.

Secondly, the arc formed between the discharge electrodes moves alongsubstantially one half the circumference of the arc extinguishingchamber as shown by a solid line in its upper section and then passesthrough the guide electrode 3 t the lower section of the chamber whereit moves along substantially one half the circumference of the chamberas shown by a broken line, so that the arc is greatly lengthened and thediameter of the chamber 1 can be greatly reduced.

It is to be understood that the invention is not limited to the specificembodiment shown and described herein, and that many changes andmodifications may be made therein without departing from the spirit ofthe invention which is defined in the appended claims.

We claim:

1. A discharging gap device comprising, in combination:

a. wall means of heat-resisting insulating material defining a chamber;

b. a partition element of said material dividing said chamber into twosections communicating through an opening in said element;

c. a guide electrode extending through said opening and havingrespective portions in said sections;

d. respective discharge electrodes spacedly juxtaposed in said sectionsto said portions; and

e. two conductors on said wall means outside said chamber andrespectively connected to said discharge electrodes.

2. A device as set forth in claim 1, wherein each discharge electrodeand the associated portion of said guide electrode constitute a pair ofgapdefining members, respective parts of said members being closestadjacent each other, the spacing of said members increasing in adirection away from said parts.

3. A device as set forth in claim 2, wherein said portions of said guideelectrode are substantially helically arcuate about an axis, and saiddischarge electrodes are spaced from the associated portions of theguide electrode in a direction away from said axis.

4. A device as set forth in claim 3, wherein said discharge electrodesare arcuate and have each a convex face opposite the associated portionsof said guide electrode.

5. A device as set forth in claim 3, wherein said wall means include twocovers of said material axially closing said chamber, and carrying saidconductors, said partition element having a tubular central portionabout said axis, two conductively connected metallic members received insaid tubular portion in abutting engagement with said coversrespectively, each metallic member and a corresponding one of saidconductors jointly constituting a capacitor, one of said covers beinginterposed between each metallic member and the corresponding conductor.

6. A device as set forth in claim 5, wherein said wall meanssubstantially close said chamber, the axial height of each sectionbetween said element and a respective cover decreasing in a directionfrom said guide electrode away from said axis.

1. A discharging gap device comprising, in combination: a. wall means ofheat-resisting insulating material defining a chamber; b. a partitionelement of said material dividing said chamber into two sectionscommunicating through an opening in said element; c. a guide electrodeextending through said opening and having respective portions in saidsections; d. respective discharge electrodes spacedly juxtaposed in saidsections to said portions; and e. two conductors on said wall meansoutside said chamber and respectively connected to said dischargeelectrodes.
 2. A device as set forth in claim 1, wherein each dischargeelectrode and the associated portion of said guide electrode constitutea pair of gap-defining members, respective parts of said members beingclosest adjacent each other, the spacing of said memBers increasing in adirection away from said parts.
 3. A device as set forth in claim 2,wherein said portions of said guide electrode are substantiallyhelically arcuate about an axis, and said discharge electrodes arespaced from the associated portions of the guide electrode in adirection away from said axis.
 4. A device as set forth in claim 3,wherein said discharge electrodes are arcuate and have each a convexface opposite the associated portions of said guide electrode.
 5. Adevice as set forth in claim 3, wherein said wall means include twocovers of said material axially closing said chamber, and carrying saidconductors, said partition element having a tubular central portionabout said axis, two conductively connected metallic members received insaid tubular portion in abutting engagement with said coversrespectively, each metallic member and a corresponding one of saidconductors jointly constituting a capacitor, one of said covers beinginterposed between each metallic member and the corresponding conductor.6. A device as set forth in claim 5, wherein said wall meanssubstantially close said chamber, the axial height of each sectionbetween said element and a respective cover decreasing in a directionfrom said guide electrode away from said axis.